To bar daughter's phone while abroad?

[MichelleC69]

So my 16 year old is in Florida with her dad. Told her specifically not to make phone calls/send texts etc and told her to switch off her data roaming, which she has done. Checked her account this morning and there are two phone calls to (or from) her dad's phone totalling up to about a tenner. I know it's only a small amount but am fuming as he's done this before whilst on holiday with her and refused to pay for the calls (he pays no maintenance, I pay for her phone and pretty much everything that she has!) I suspect it's him who has made the calls to her phone as she knows not to use it. So I called O2 and had them bar her phone from making or receiving phone calls until I ask them to unbar it! Am I being mean?

I wouldn't block it, what if there was an emergency and she needed to use her phone for help?
It's all very well saying "there's loads of wifi about" but not every area has it.
Even in built up areas and cities. You'd have to find the nearest building or whatever that has it in order to connect (I know, as I use free wifi instead of data)
I wouldn't risk her not being able to phone for help if she needs it.

Update: apparently they were Whatsapp calls. But what neither of them knew (until I just told them) is that if the wifi signal isn't good enough, the app automatically directs the call to an international call!